A transmission having a selective-sliding transmission mechanism in which operation of a lever causes a main gear to engage with a selected gear is disclosed, for example, in Japanese Utility Model Laid-Open Publication No. HEI-6-43561.
This transmission using the selective-sliding transmission mechanism will be described with reference to FIGS. 29 and 30.
The transmission shown in FIG. 29 includes an input shaft 402 as a first shaft, second shaft 403, third shaft 404 and output shaft 405 which are rotatably supported in a case 401.
On the input shaft 402, gears 406 and 407 are mounted. On the second shaft 403, gears 408 and 409 are rotatably mounted in constant mesh with the gears 406 and 407. A mechanical clutch 410 for selectively connecting the second shaft 403 to either of the gears 408 and 409 is provided between the gears 408 and 409 on the second shaft 403.
A sliding gear 413 is slidably spline-coupled to the second shaft 403. A loose-fit gear 414 is rotatably mounted on the second shaft 403.
A transmission gear 415 is rotatably mounted on the input shaft 402. The transmission gear 415 includes a gear 415a configured to be engaged or disengaged by slide of the sliding gear 413 and a gear 415b constantly engaging the loose-fit gear 414.
Reference numeral 416 denotes an operating fork for moving the sliding gear 413.
A gear-sliding first sub transmission mechanism 417 for providing two different speeds to the transmission gear 415 by sliding control of the sliding gear 413 consists of the sliding gear 413, loose-fit gear 414 and transmission gear 415.
Referring to FIG. 30, a guide hole 424 in which a main shift lever 422 moves has a horizontal H shape. In the upper side of the guide hole 424, reverse travel, first forward gear, neutral and second forward gear positions are set sequentially from the right end.
Referring to FIG. 29, in the sliding-type first sub transmission mechanism 417, that is, in the selective-sliding transmission mechanism, when the sliding gear 413 rotating with the second shaft 403 and engaging with the loose-fit gear 414 moves rightward in the figure to engage with the transmission gear 415, the sliding gear 413 and the transmission gear 415 cannot easily come into engagement because they are on the different rotating shafts (specifically, second shaft 403 and input shaft 402), being likely to cause noise or tooth wear.
In the transmission pattern shown in FIG. 30, the first forward gear position and the second forward gear position are on the opposite sides of the neutral position. It is thus necessary to control the main shift lever 422 through the neutral position to shift from first forward gear to second forward gear for increasing speed.
If the main shift lever 422 can be controlled without passing through the neutral position, shift between first forward gear and second forward gear is made smoothly, improving the operability. Improved engagement between the gears 413 and 415 further allows shifting without being caught in each gear position, leading to more smooth operation of the main shift lever 422.
It is also possible to interpose a synchromesh transmission mechanism which effects engagement upon synchronization in rotation between the sliding gear 413 and the transmission gear 415, for example, if the gears 413 and 415 cannot easily engage with one another as described above. The synchromesh transmission mechanism, however, has a large number of components whose shapes are complicated, leading to cost and weight increases.
It is thus desired to improve a transmission to increase the operability of a shift lever while limiting increases in cost and weight.